1. Field of the Invention
The present invention relates to a time lapse videocassette tape recorder (VCR) used for security and/or surveillance, and more particularly to an improved picture signal record/playback apparatus and method thereof for a time lapse VCR which makes it possible to operate with an enhanced stability and greater accuracy in providing picture signals.
2. Description of the Prior Art
In general, a time lapse VCR is adopted in sites such as banks, museums and the like to prevent undesirable trespassing.
Here, a time lapse VCR plays a watchdog role while recording or playing-back, and in case there are installed several video cameras, there accordingly should be provided as many time lapse VCRs, so that an input picture signal can be converted and recorded in a VCR via a buffer memory in the VCR.
A time lapse VCR used for a watchdog and observation purpose over a long time base does not record all the frames during a real running time period of a picture signal, and instead selects a certain interval among real running time periods and records corresponding frames one by one, whereby stationary pictures can be repeatedly recorded at a certain time intervals while running a tape at a constant rate.
As shown in FIG. 1, a conventional multi-picture signal recording apparatus includes: a microprocessor 10 for carrying out a general control in accordance with a time-sharing signal CVS; a switch SW1 for selecting input picture signals VS1-VS4 in accordance with a control signal CS0 from microprocessor 10; an A/D converter 11 for converting a picture signal selected by switch SW1 into a digital signal; four field memories 12A-12D for respectively storing therein a corresponding output value of A/D converter 11 in accordance with control signals CS1-CS4 outputted from microprocessor 10; a switch SW2 for selecting output values of the four field memories 12A-12D in accordance with control signal CS0 from microprocessor 10; a D/A converter 13 for converting an output value selected by switch SW2 into an analog signal; a luminance signal record processing unit 14 and a color signal record processing unit 15 for respectively separating and recording a luminance signal and a color signal from the analog picture signal outputted from the D/A converter 13; an adder 16 for adding output signals of luminance signal record processing unit 14 and color signal record processing unit 15; a record amplifier 17 for amplifying and applying to a video head VHD a picture signal outputted from the adder 16; a voltage controlled oscillator (VCO) 18 for oscillating a frequency in accordance with control signal CS0 outputted from microprocessor 10; and a control signal record processing unit 19 for processing and applying to a control head CDH an output signal of VCO 18.
The operation of the thusly constituted conventional multi-picture signal recording apparatus will now be described with reference to the accompanying drawings.
First, as shown in FIGS. 2A-2F, when time-sharing signal CVS is applied, the microprocessor 10 outputs control signal CS0 as shown in FIG. 2B, and control signals CS1-CS4 as shown in FIGS. 2C-2F.
The switch SW1 connects an operating terminal all sequentially to fixed terminals b11-b14 in accordance with the control signal CS0 and outputs picture signals VS1-VS4. The selected picture signals are converted to digital signals in A/D converter 11 and applied sequentially to the four field memories 12A-12D which sequentially store therein the applied digitized field picture signals VS1-VS4 in accordance with control signals CS1-CS4, and the switch SW2 connects an operating terminal a21 sequentially to the fixed terminals b21-b24 in accordance with control signal CS0, whereby the picture signals VS1-VS4 outputted from the field memories 12A-12D are sequentially converted to analog signals in D/A converter 13.
As a result, analog picture signals outputted from the D/A converter 12 are separated into luminance signals and color signals via the luminance record processing unit 14 and the color record processing unit 15 and added in the adder 16. The added picture signals are amplified in the record amplifier 17, applied to video head VHD, and recorded on the video tape.
The VCO 18 outputs a separation control signal in accordance with control signal CS0 outputted from microcomputer 10. The control signal record processing unit 19 processes and applies the separation control signal to control head CDH thus to be recorded on the video tape.
As shown in FIG. 3, picture signals VS1-VS4 are sequentially and circulatedly recorded on slant tracks of the video tape, and separate control signals F1-F4 are synchronized in accordance with picture signals VS1-VS4 and recorded on a linear track on a lower portion of a video tape.
Namely, the multi-picture signal recording apparatus selects a certain interval during real time in accordance with time-sharing signal CVS and records a picture signal frame by frame.
As shown in FIG. 4, a conventional multi-picture signal playback apparatus includes: a pre-amplifier 20 for amplifying separation control signals F1-F4 played back from a video tape by a control head CDH; a waveform shaper 21 for shaping a pulse wave outputted from the pre-amplifier 20 into a sine wave; a frequency discriminator 22 for discriminating a frequency of an output signal of the waveform shaper 20; a microprocessor 23 for outputting control signals CS11-CS14 in accordance with a discrimination signal from the frequency discriminator 22; a picture signal pre-amplifier 24 for amplifying multi-picture signals VS1-VS4 played back from the video tape by video head VHD; a luminance signal demodulator 25 and a color signal demodulator 26 for respectively demodulating a luminance signal and a color signal amplified in the picture signal pre-amplifier 24; an adder 27 for adding the luminance signal and the color signal demodulated by the luminance signal demodulator 25 and the color signal demodulator 26, respectively; an A/D converter 28 for converting an output signal of adder 27 into a digital signal; four field memories 29A-29D for storing a digital picture signal outputted from the A/D converter 28 in accordance with control signals CS11-CS14 outputted from microprocessor 23; a picture signal processing unit 30 for processing picture signals outputted from the four field memories 29A-29D to thereby appear on the same picture; and a D/A converter 31 for converting a digital picture signal outputted from the picture signal processing unit 30 into an analog signal.
The operation of the thusly constituted conventional multi-picture signal playback apparatus will now be described with reference to the accompanying drawings.
First, separation control signals F1-F4 played back by control head CDH from a linear track of the video tape are amplified in the pre-amplifier 20, and demodulated in the waveform shaper 21. The frequency discriminator 22 receives demodulated and control signals F1-F4 and discriminates their frequencies, thereby outputting a discrimination signal indicating the separation of multi-picture signals VS1-VS4.
The picture signals VS1-VS4 played back by video head VDH from slant tracks of the video tape are amplified in the picture signal pre-amplifier 24, and the amplified picture signals are demodulated into a luminance signal and a color signal via luminance signal demodulator 25 and color signal demodulator 26. The demodulated luminance signal and color signal are added in the adder 27 and converted into a digital signal in the A/D converter 28.
As a result, microprocessor 23 controls the operation of field memories 29A-29D in accordance with the discrimination signal outputted from the frequency discriminator 22, and the field memories 29A-29D store therein and output a digital picture signal outputted from the A/D converter 28 in accordance with control signals CS11-CS14, thereby separating the played-back multi-picture signals VS1-VS4.
The multi-picture signals VS1-VS4 outputted from the field memories 29A-29D are added in picture signal processing unit 30 so as to be displayed on the same picture, wherein the picture signal processing unit 30 processes the picture signals by using a PIP (picture in picture) method and outputs the applied multi-picture signals VS1-VS4, whereby a plurality of picture signals can be separately displayed on a single picture.
As described above, the conventional multi-picture signal record/playback apparatus selects a certain interval during real time in accordance with a time-sharing signal CVS and records a picture signal, and the recorded picture signal is played back and displayed in the form of a plurality of picture signals.
However, a tape-recording time has limitation with regard to a multi-picture recording, and when repeating a stop mode recording and a two-track running there are required a variety of controls for frequently and precisely moving an instrumental driving apparatus except for a tape running system and accordingly it is complicated and high priced. Also, in a state in which a tape is loaded for a long time, if a recording and playback operation are repeatedly carried out many times, damage to the VCR or the tape may be incurred thereby.
Further, in case of a VHS tape having a track pitch of 58 m.mu.m, the design of the mechanism incurs higher cost and lower productivity, and the conventional multi-picture signal record/playback apparatus does not provide a long time recording function and a tape recorded by time lapse recording can not be accurately played back via a general VCR.